This invention relates to construction panels for structural support systems having high strength to weight ratios and excellent insulating properties. The construction panels may be used to build walls, floors, roofs, exterior fascia panels, facades, curtain walls, spandrels, balcony dividers, interior partitions, ceilings, etc. for industrial, commercial and residential buildings.
Traditionally, buildings have been constructed from a wide variety of materials. Among the more common are wood, cinder block, brick, concrete, metal, and glass. Each has particular advantages and disadvantages. Wood, while relatively easy to work with, is quite flammable, requires the labor of skilled carpenters who take a long time in constructing an entire building, and is becoming increasingly expensive. Cinder block and brick are both quite heavy, resulting in high transportation costs and require the work of skilled masons over a long period of time to construct a building therefrom. Concrete is difficult to transport, fairly expensive and requires the use of special techniques and equipment, in order to produce a building therefrom. Metal panels are not good insulators and require the services of welders, riveters or other personnel to fasten the panels together and to the supporting structure by bolts, rivets or the like. Glass is breakable, hard to transport and is not a good insulator. Because of these disadvantages, new materials have been and are being developed to replace the traditional building materials.
There is an increasing awareness that the world's natural resources must be conserved for future generations. The importance of adequately insulating buildings has been stressed by government and private industry alike. By properly insulating a building, consumers of energy used to heat and cool the building may save money, while at the same time aiding to conserve natural resources. In addition, by reducing energy demands to heat and cool our homes, offices, factories and the like, the citizens of the U.S. can help reduce our country's dependence on imported oil and natural gas.
Various methods of insulating buildings have been proposed. Rolls of insulating material having various degrees of thicknesses may be purchased and unrolled at the job site adjacent the wall, floor, and roof members to be insulated. For pre-constructed structures, insulating material may be blown between the outer facing and the inner walls of a building to the desired density.
Another technique of providing adequate insulation for buildings is to incorporate insulating material in prefabricated building panels. These panels offer the advantages of good insulating properties, mass production, and ease of on-site assembly of the panels, among others. These panels generally comprise a core of insulating material surrounded by structurally rigid panels. The core of insulating material may comprise balsa wood, glass wool, foamed or expanded polymeric materials such as polystyrene, polyvinyl chloride, polyurethane, etc. The core material may be surrounded by panel members comprising first and second major face members and side and end walls of such materials as plywood, metal, resin, and resin reinforced with fibrous glass rovings, etc. Generally, these panels are strong, lightweight and provide excellent insulating properties.
These modular panels also have some disadvantages. Since the foam used in forming the core is not elastic, once it is compressed, a space develops between the core and facing member. This results in weakened structural integrity and may be responsible for such conditions as warping, buckling and cracking of the face member or of the entire panel. An additional advantage is that the major face members generally cannot withstand a great amount of load bearing pressure as may be encountered when the panels are used as part of a floor or, in some climates, a roof. To make the panels stronger, various reinforcing means have been incorporated within them. The following patents are representative of the way in which the prior art has attempted to overcome the problems and disadvantages associated with foamed core sandwich-type panels.
Boyer, in U.S. Pat. No. 2,376,653, discloses a laminated panel comprising a thermoset resin containing reinforcing materials such as sisal, cocoanut shell fibers, wood excelsior, etc. bonded between two fibrous sheets. Spacers of wood or synthetic thermoset resin are placed between the inner surfaces of the spaced sheets to offset any tendency of the panel to buckle or warp.
Shwayder, in U.S. Pat. No. 2,880,473, discloses a fibrous glass lamination comprising a core of hard rigid material, such as Masonite, kraft paper, heavy carboard, sheet steel, etc., encased within a thin skin of bibrous glass which acts to resist the tension of bending forces upon the laminate. Reinforcing bars or tubes may be located within the inner layer. Other embodiments show reinforcing bars extending from the inner surface of the fibrous glass coating out of the laminate. The reinforcing bars or tubes extending from the face of the laminate are parallel to each other so that one laminate may be interlocked with another laminate.
Weinrott, in U.S. Pat. No. 3,462,897, discloses a panel structure comprising a frame made of wood to which are attached outer skins made of plywood or asbestos. Urethane foam is injected under pressure and heat into the cavities formed by the skins and the frame to form a core which adheres to all of the surfaces in contact therewith so that the resultant panel structure is a stressed skin structure. The panels may be used for walls, floors, or roofs and are particularly adapted for onsite assembly into a building.
Andersen, in U.S. Pat. No. 3,573,144, discloses a sandwich-type structural panel wherein face sheets of woven glass cloths impregnated with an epoxy or polyester resin are bonded to a core. The core comprises a plurality of spacer blocks made of balsa wood or foamed polymeric material. The spacer blocks are connected to each other by undulating strips of resin impregnated fibrous webs, wherein the fiber is glass fiber or other natural or synthetic, organic or inorganic material. Reinforcing strips of the same type of resin impregnated fibrous material may be placed between adjacent spacer blocks to further strengthen the panel.
Payne, in U.S. Pat. No. 3,733,232, discloses a composite building panel wherein a variety of base sheet materials, such as sheet steel, plaster board, asbestos felt or the like, may be combined with outer facing sheets of metal or other suitable material by means of a foamed or expanded plastic core. The facing sheet is preferably corrugated and the foamed plastic material may be foamed polyurethane.
Allard, in U.S. Pat. No. 3,791,912, discloses a sandwich-type construction panel wherein reinforcing bars of metal are placed between a foam core and covering material comprising resin incorporated with glass fibers. The core or body is formed from an extruded block of foamed polymeric material, such as polyvinyl chloride or polyurethane. The core or body of foamed polymeric material has grooves cut into its surface according to the dimensions of the metal reinforcing bars, such as those used in reinforced concrete construction, but these are not prestressed. The resin coating includes flexible glass fibers disposed in several layers within the resin covering. The resin covering is applied to the core or body such that the metal reinforcing rods are between the core and the resin covering. Allard also discloses several other embodiments of building panels based on the concept of using metal reinforcing rods with foamed polymeric material sandwich-type structures.
Watkins et al., in U.S. Pat. No. 3,898,115, disclose a sandwich-type building panel comprising a sheath of resin reinforced with glass fibers filled with a self-foaming polyurethane which forms the inner core. Voids may be left within the inner core to provide for channels for electrical wiring, water pipes or air conduits. In an alternate embodiment, the core is W-shaped. A plurality of triangular foam blocks are placed between two mats of woven glass fibers. The top mat is stitched to the bottom mat adjacent the base of each foam block and covers the apex of the foam blocks. Another layer of oppositely disposed triangular foam blocks are placed on top of the second layer immediately after the second mat has been sprayed or impregnated with a resin. A third mat of woven glass fibers is placed over the second layers of blocks and impregnated with resin. The entire core structure is then sandwiched between two sheets of resin impregnated with glass fibers. In either of the embodiments, the panels may be joined together along their coacting edges by means of a plurality of bolts, rivets or other fasteners through holes in flanges formed in the edges of the panels.
Johnson, in U.S. Pat. No. 3,920,871, discloses a structural element particularly suitable for forming curved structures, such as boat hulls. The structural element comprises parallel rows of alternately oppositely undulated bundles of glass fiber rovings which are woven over and under adjacent parallel foamed plastic slats. The rovings are loosely woven so that there are spaces between the adjacent foamed plastic slats to allow for curvature of the structural element. Face sheets of woven glass fibers or other woven materials are placed on either side of the structure. A settable resin is then used to impregnate the woven structural elements so that all voids between the woven rovings, the woven face sheets and the foamed plastic slats are filled with the settable resin. The impregnation of the structural element with the settable resin produces upon setting "I-beams" of resin between the foamed plastic slats and provides a surface coating of resin which is integral with the "I-beams", to provide a strong, rigid, unitary structure.